Method and system for detecting diagonal strength of an edge in an image

ABSTRACT

A system and method that determines the strength of an edge in a video image using a gradient of the edge in a first direction and a gradient of the edge in a second direction. The system uses the gradient in the first direction and the gradient in the second direction to approximate a distance function to determine the strength of the edge. A programmable threshold may be used in the determination, where an edge is treated like it does not exist if the distance is less than the threshold. The distance function may be an approximation of the Cartesian distance function.

RELATED APPLICATIONS

This patent application makes reference to, claims priority to andclaims benefit from U.S. Provisional Patent Application Ser. No.60/540,826, entitled “Method and System for Motion Adaptive Deinterlacerwith Integrated Directional Filter,” filed on Jan. 30, 2004, thecomplete subject matter of which is hereby incorporated herein byreference, in its entirety.

This application makes reference to:

-   U.S. patent application Ser. No. 10/314,525 filed Dec. 9, 2002;-   U.S. patent application Ser. No. 10/945,769 filed Sep. 21, 2004;-   U.S. patent application Ser. No. 10/875,422 filed Jun. 24, 2004;-   U.S. patent application Ser. No. 10/945,619 filed Sep. 21, 2004;-   U.S. patent application Ser. No. 10/945,587 filed Sep. 21, 2004;-   U.S. patent application Ser. No. 10/871,758 filed Jun. 17, 2004;-   U.S. patent application Ser. No. 10/945,796 filed Sep. 21, 2004;-   U.S. patent application Ser. No. 10/945,817 filed Sep. 21, 2004;-   U.S. patent application Ser. No. 10/945,729 filed Sep. 21, 2004;-   U.S. patent application Ser. No. 10/945,828 filed Sep. 21, 2004;-   U.S. patent application Ser. No. 10/946,152 filed Sep. 21, 2004;-   U.S. patent application Ser. No. 10/946,153 filed Sep. 21, 2004; and-   U.S. patent application Ser. No. 10/871,649 filed Jun. 17, 2004.

The above stated applications are hereby incorporated herein byreference in their entirety.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[Not Applicable]

MICROFICHE/COPYRIGHT REFERENCE

[Not Applicable]

BACKGROUND OF THE INVENTION

In the field of video compression, communication, decompression, anddisplay, there has been for many years problems associated withsupporting both interlaced content and interlaced displays, along withprogressive content and progressive displays. Many advanced videosystems support either one or the other format. As a result such devicesas deinterlacers have become important components in many video systems.Deinterlacers convert interlaced video format into progressive videoformat.

Deinterlacing takes interlaced video fields and coverts them intoprogressive frames, at double the display rate. Certain problems mayarise concerning the motion of objects from image to image. Objects thatare in motion are encoded differently in interlaced fields fromprogressive frames. Video images, encoded in deinterlaced format,containing little motion from one image to another may be deinterlacedinto progressive format with virtually no problems or visual artifacts.However, problems arise with video images containing a lot of motion andchange from one image to another, when converted from interlaced toprogressive format. As a result, some video systems were designed withmotion adaptive deinterlacers.

Today, motion adaptive deinterlace video systems rely on multiple fieldsof data to extract the highest picture quality from a video signal. Whenmotion is detected between fields, it may be very difficult to usetemporal information for deinterlacing. Instead, a deinterlacing circuitmust utilize a spatial filter (usually a vertical filter of the field ofinterest). However, often the source material has diagonal lines, orcurved edges, and using a spatial filter may not yield satisfactoryresults. For example, diagonal or curved edges will be represented withstair-step or jaggies that are visible in the image.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with some aspects of the present invention asset forth in the remainder of the present application with reference tothe drawings.

BRIEF SUMMARY OF THE INVENTION

Aspects of the present invention may be seen in a system and method thatdetermines the strength of an edge in a video image using a gradient ofthe edge in a first direction and a gradient of the edge in a seconddirection. The method comprises approximating the distance functionusing the gradient in the first direction and the gradient in the seconddirection; comparing the distance to a programmable threshold; anddetermining the strength of the edge based on the result of thecomparison.

The edge may be treated like there is no edge when the distance is lessthan the threshold.

The system comprises circuitry capable of performing the method asdescribed hereinabove that determines the strength of an edge in a videoimage.

These and other features and advantages of the present invention may beappreciated from a review of the following detailed description of thepresent invention, along with the accompanying figures in which likereference numerals refer to like parts throughout.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A illustrates a block diagram of an exemplary architecture forpositioning of a MAD-3:2, in accordance with an embodiment of theinvention.

FIG. 1B illustrates a block diagram of exemplary interfaces for theMAD-3:2 shown in FIG. 1A, in accordance with an embodiment of theinvention.

FIG. 1C illustrates a block diagram of an exemplary flow of thealgorithm, which may be utilized by the MAD-3:2 of FIG. 1A and FIG. 1B,in accordance with an embodiment of the invention.

FIG. 2 illustrates a block diagram of an exemplary directional filterthat may be integrated into a motion adaptive de-interlacer and utilizedfor motion adaptive deinterlacing with integrated directional filtering,in accordance with an embodiment of the present invention.

FIG. 3 illustrates a block diagram of an exemplary angle detection blockthat may be integrated in a directional filter and utilized for motionadaptive deinterlacing with integrated directional filtering, inaccordance with an embodiment of the present invention.

FIG. 4 illustrates a block diagram of an exemplary diagonal filter blockthat may be integrated in a directional filter, in accordance with anembodiment of the present invention.

FIG. 5 illustrates a graphical representation that may be utilized inconnection with distance approximation, in accordance with an embodimentof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Aspects of the present invention relate to processing video signals.More specifically, certain embodiments of the invention relate to amethod and system for implementation of a distance function to determinethe strength of an edge in a video image. Although the followingdiscusses an embodiment of the invention with respect to videoprocessing and the Cartesian distance function, it should be understoodthat the present invention may be modified for use in any systemrequiring determination of distance functions and/or similarmathematical functions.

Certain aspects of the invention may comprise methods and systems for amotion adaptive deinterlacer (MAD) capable of reverse 3:2 pull-down and3:2 pull-down with cadence detection, which may be referred to asMAD-3:2 or MAD32, that may be utilized in a video network (VN). Thealgorithms and architectures for the motion adaptive deinterlacer may beadapted to acquire interlaced video fields from one of a plurality ofvideo sources in the video network and convert the acquired interlacedvideo fields into progressive frames, at double the display rate, in avisually pleasing manner.

The motion adaptive deinterlacer (MAD-3:2) may be adapted to acceptinterlaced video input from a video bus (VB) and output deinterlaced,progressive video to the video bus (BUS) utilized by the video network.The motion adaptive deinterlacer may accept, for example, 720×480i andproduce, for example, 720×480p in the case of NTSC. For PAL, the motionadaptive deinterlacer (MAD) may accept, for example, 720×576i andproduce, for example, 720×576p. Horizontal resolution may be allowed tochange on a field-by-field basis up to, for example, a width of 720. Themotion adaptive algorithm utilized by the motion adaptive deinterlacer(MAD-3:2) may be adapted to smoothly blend various approximations forthe missing pixels to prevent visible contours produced by changingdecisions.

A plurality of fields of video may be utilized to determine motion. Forexample, in an embodiment of the invention, five fields of video may beutilized to determine motion. The motion adaptive deinterlacer (MAD) mayproduce stable non-jittery video with reduced risk of visual artifactsdue to motion being misinterpreted while also providing improved stillframe performance. The motion adaptive deinterlacer (MAD-3:2) may alsoprovide additional fields per field type of quantized motioninformation, which may be selectable in order to reduce the risk ofmisinterpretation. For example, up to three (3) additional fields ormore, per field type, of quantized low-cost motion information mayoptionally be selected in order to reduce risk of misinterpreted motioneven further. This may provide a total historical motion window of upto, for example, 10 fields in a cost effective manner. Integratedcross-chrominance removal functionality may be provided, which may aidin mitigating or eliminating NTSC comb artifacts. A directional compassfiltering may also be provided in order to reduce or eliminate jaggiesin moving diagonal edges. The MAD-3:2 may provide reverse 3:2 pull-downfor improved quality from film-based sources.

In accordance with another aspect of the invention, the algorithms andarchitectures for the motion adaptive deinterlacer (MAD) may also beadapted to provide bad-edit detection in order to ensure a visuallypleasing transition to new cadence in situations where editing may havebeen carelessly performed. Furthermore, per-pixel correction may also beprovided to improve the quality of subject matter containing both filmand video at the same time. For example, per-pixel correction may beutilized for interlaced titles, which have been overlaid on film-basedcontent. The motion adaptive deinterlacer (MAD-3:2) may also provideoptional CPU control over, for example, 3:2 and/or 2:2 cadence detectionand correction.

FIG. 1 a is a block diagram of an exemplary architecture illustratingthe positioning of a MAD-3:2 100, in accordance with an embodiment ofthe present invention. Referring to FIG. 1 a, the MAD-3:2 100 along witha plurality of scalers (102, 104, 106, and 108), for example, may bepositioned between a first crossbar 110 and a second crossbar 112. Thefirst crossbar 110 may be referred to as an input crossbar and thesecond crossbar 112 may be referred to as an output crossbar.

The MAD-3:2 100 may comprise at least one video network input and atleast one video network output and may be configured to maintain its ownadditional field stores. A feedback path may be provided from the outputof the second crossbar 112 to the input of the first crossbar 110. Thismay allow any of the standard definition (SD) video sources such as theMPEG feeders 103 and 105, video feeders 107, 109, 111, 113 and 115,and/or VDEC 117, and so on, to function as an input to the MAD32 100and/or one of the scalers 102, 104, 106, and 108. The VDEC 117 may be ananalog video decoder that may process NTSC signals to separate colorfrom luma. The MPEG feeders 103 and 105 may accept 4:2:0 and 4:2:2 videodata and supply 4:2:2 video data. The video feeders 107, 109, 111, 113and 115, may accept 4:2:2 video data and supply 4:2:2 video data. Theoutput of the second crossbar 112 may be passed back to the firstcrossbar 110 via the feedback path 114.

U.S. patent application Ser. No. 10/314,525 filed Dec. 9, 2002 entitled“Network Environment for Video Processing Modules” discloses anexemplary crossbar network module and associated system, which isrepresentative of the video network crossbar that may be utilized inconnection with the present invention. Accordingly, U.S. patentapplication Ser. No. 10/314,525 filed Dec. 9, 2002 is herebyincorporated herein by reference in its entirety.

FIG. 1 b is a block diagram illustrating exemplary interfaces for theMAD-3:2 100 shown in FIG. 1 a, in accordance with an embodiment of thepresent invention. Referring to FIG. 1 b, the MAD-3:2 100 may comprise aplurality of bus interfaces and may include the capability to generateone or more system CPU interrupts. The MAD-3:2 100 may run on, forexample, a single system clock. However, the invention may not be solimited and more than one clock may be utilized. In one embodiment ofthe invention, the MAD-3:2 100 may include a video bus (VB) input 120, avideo bus output 122, and, for example, two independent bidirectionalread/write SCB client connections, SCB0 124 and SCB1 126. The SCB may bean internal bus utilized to access frames/fields stored in the memory.The video bus (VB) input 120 may be utilized for supplying fields to theMAD-3:2 100. The video bus output 122 may allow the deinterlaced outputframes to be transferred throughout the video network and pass through ascaler before reaching a composite or capture block. An RBUS interface128 may be utilized to configure the MAD-3:2 100 or to access its statusvia one or more interface signals and/or registers. The RBUS may be ageneral-purpose bus utilized for programming registers for control andconfiguration of the CPU. At least a portion of the interfaces of theMAD-3:2 100 may be synchronous to a clock input of the scaler. A videonetwork receiver input error interrupt 130 may be generated on an inputfield size, which may differ from a programmed field size, which isexpected. An inverse telecine ready interrupt 132 may be generated forevery field, or at least some fields, at the point in time when thestatistics gathered in the previous field are ready to be read by a CPUor other processor.

FIG. 1 c is a block diagram illustrating an exemplary flow of thealgorithm which may be utilized by the MAD-3:2 100 of FIG. 1 a and FIG.1 b, in accordance with an embodiment of the present invention.Referring to FIG. 1 c, there is shown a data flow corresponding to thealgorithm utilized for deinterlacing the luma component of video. Thealgorithm may effectively be divided into two sub-blocks. For example,diagrammed on the left of FIG. 1 c is the motion adaptive deinterlacer(MAD) method of deinterlacing 150 and on the right, there is shown thereverse 3:2 pulldown method 180. For every output pixel, motion adaptivedeinterlacing 150, reverse 3:2 pulldown 180, or a blend 160 of motionadaptive deinterlacing and reverse 3:2 deinterlacing may be utilized todetermine a motion-adapted value of the output pixel underconsideration.

The motion adaptive deinterlacer (MAD) 150 may comprise a directionalfilter 154, a temporal average 156, and a blender 158. The MAD 150 maycomprise suitable logic, code, and/or circuitry and may be adapted forperforming the MAD method of deinterlacing. A processor may be adaptedto perform the operation of the MAD 150. The MAD 150 may comprise localmemory for storage of data and/or instructions. The directional filter154 may comprise suitable logic, code, and/or circuitry and may beadapted for spatially approximating the value of the output pixel. Thetemporal average 156 may comprise suitable logic, code, and/or circuitryand may be adapted for temporal approximation of the value of the outputpixel. The blender 158 may comprise suitable logic, code, and/orcircuitry and may be adapted to combine the temporal and spatialapproximations of the value of the output pixel.

In operation, the MAD 150 may receive input field pixels from aninterlaced video field and convert them into output frame fields in aprogressive frame, at double the display rate. The horizontal resolutionof the input to the MAD 150 may change on a field-by-field basis. TheMAD 150 may utilize a motion adaptive algorithm that may smoothly blendvarious approximations for the output pixels to prevent visiblecontours, which may be produced by changing decisions. In an embodimentof the present invention, it may be necessary to determine the amount ofmotion around each output pixel, to use an appropriate approximation forthe output pixel. The MAD 150 may utilize the directional filter 154,the temporal average 156, and the blender 158 to obtain a motion-adaptedvalue for the output pixel that is visually pleasing.

FIG. 2 illustrates a block diagram of an exemplary directional filter200 that may be integrated into a motion adaptive de-interlacer andutilized for motion adaptive deinterlacing with integrated directionalfiltering, in accordance with an embodiment of the present invention.The directional filter 200 may be, for example, the directional filter154 of the MAD 150 of FIG. 1 c. A plurality of pixels may be read fromline buffers every cycle and processed at the clock rate. For example,four pixels 201, 203, 205 and 207 may be read from the line buffersevery cycle and processed at the clock rate. The pixels may be arrangedin, for example, a vertical order H, E, F, J from top to bottom. Thecurrent pixel O, which is missing, or part of an absent line in theinterlaced field. Pixels E and F may be directly above and below pixelO, in the present lines in the interlaced field, and pixels H and J maybe the pixels directly above pixel E and below pixel F in present linesin the interlaced field. U.S. patent application Ser. No. 10/945,796filed Sep. 21, 2004 entitled “Pixel Constellation for Motion Detectionin Motion Adaptive Deinterlacer” discloses an exemplary pixelconstellation that may be utilized in connection with the presentinvention for pixels H, E, F, and J. Accordingly, U.S. ProvisionalPatent Application Ser. No. 10/945,796 filed Sep. 21, 2004 is herebyincorporated herein by reference in its entirety.

The directional filter 200 may receive the pixels 201, 203, 205 and 207from the line buffers, and produce a spatial average using a process ofadaptive diagonal filtering. The directional filter 200 may comprise anangle detection block 209 and a diagonal filter block 211. The angledetection block 209 may examine an array of pixels to determine theangle and strength of gradients in the source picture. The diagonalfilter block 211 may utilize an array of pixels and the angleinformation 215 outputted by the angle detection block 209 to select oneof a plurality of filter kernels and blend the resulting diagonal filterwith a vertical FIR based on the strength of the diagonal information217 outputted by the angle detection block 209. The resulting output 213may be used as a spatial average in the motion adaptive de-interlacer(MAD).

Filtering in the directional filter 200 may be performed on field dataentirely within a field. As a result the directional filter 200 may beimmune from motion artifacts. Additionally, there may be no motion inthe MAD, in which case the output spatial average 213 may not be usedelsewhere in the MAD. As a result the diagonal filter 200 may onlyaffect images with motion.

FIG. 3 illustrates a block diagram of an exemplary angle detection block300 that may be integrated in a directional filter and utilized formotion adaptive deinterlacing with integrated directional filtering, inaccordance with an embodiment of the invention. The angle detectionblock 300 may be, for example, the angle detection block 209 of thedirectional filter 200 of FIG. 2. The angle detection block 300 mayoutput an angle select signal 317 and a diagonal strength signal 315 perclock cycle. The angle detection block 300 may comprise a delta x (dx)kernel and a delta y (dy) kernel, comparison block 305 for angleselection; and distance approximation block 307 with a threshold block309 for diagonal strength determination.

Delta x (dx) kernel and delta y (dy) kernel may be computed using avertical and horizontal edge detectors 301 and 303 respectively on, forexample, a 3×2 array of pixels from lines E and F. Ultimately, thevertical edge detector 301 may determine the gradient in they-direction, which may indicate whether there is a change in thevertical direction in a field. Similarly, the horizontal edge detector303 may determine the gradient in the x-direction, which may indicatewhether there is a change in the horizontal direction in the field. Thedx kernel may be represented as:[½, 0, −½][½, 0, −½]The dy kernel may be represented as:[¼, ½, ¼][−¼, −½, −¼]A partial crossbar may be utilized to repeat pixels at the boundariesbefore they are multiplied. A gradient in both the x- and y-directionsmay indicate the presence of a diagonal edge. A gradient in only thex-direction may indicate the presence of a vertical edge, and a gradientin only the y-direction may indicate the presence of a horizontal edge.

The comparison block 305 may receive scaled values 321 and 323 of abs|dx| and abs |dy| respectively, as well as a sign value 319 to determinethe angle of the gradient in the source image. The case selection usingcomparisons of |dx| and |dy| may be accurate to within, for example,about 0.001 radians of a true arc-tangent (arctan) function, but may beconsiderably cheaper. A modification to a true absolute value may bemade to prevent overflow. When the delta x kernel dx=(−256), theabsolute value |dx|=255. Similar absolute value operation for |dy| maybe used.

U.S. patent application Ser. No. 10/946,153 filed Sep. 21, 2004 entitled“Interpolator Direction Selection” discloses a method for determiningthe direction and angle of an edge using |dx| and |dy|. Accordingly,U.S. patent application Ser. No. 10/946,153 filed Sep. 21, 2004 ishereby incorporated herein by reference in its entirety.

The resulting angle selection value 317 may result in a selection of oneof, for example, 7 filter kernels comprising {NWW, NW, NNW, N, NNE, NE,NEE} each indicating a direction corresponding to the resulting angle.An additional filter kernel HOR may be utilized for horizontalfiltering. Similar results may be achieved using the N filter in thiscondition. The comparison block 305 may produce one angle selection percycle.

The distance approximation block 307 may determine the strength of thediagonal, which may be determined using the Cartesian distance:d=√{square root over (dx ² +dy ²)}The ideal distance equation may be complicated to realize with simplehardware because of the squares and square root. Instead, anapproximation may be implemented utilizing simpler methods to determinethe distance value with the following function:d=MAX(|dx|,|dy|)+MIN(|dx|,|dy|)/4The above function may be implemented with different combinations ofmultiples of the MIN and MAX values other than ¼ and 1, respectively, toapproximate the Cartesian distance function.

FIG. 5 illustrates a graphical representation that may be utilized inconnection with distance approximation, in accordance with an embodimentof the present invention. Using the above approximation, the result forthe distance is very close to the Cartesian distance function asillustrated in FIG. 5. The x-axis 501 corresponds to the values of dx asthey go from 1 down to 0 and dy from 0 to 1 according to the Cartesianformula (dy=√(1−dx²), and the y-axis 503 illustrates the distance withthe dotted line 505 illustrating the Cartesian distance and the solidline 507 illustrating the approximation. The deviation of theapproximation from the ideal may be minimal with a maximum deviation ofaround 10% where both dy=dx=1/√2≈0.707.

The diagonal strength determination may utilize a diagonal gain (DG)control parameter 311 used in the distance approximation block 307, anda diagonal threshold (TH) parameter 313 used in the threshold block 309.The value of DG 311 may be in the range {0-15}, and the value of TH 313may be in the range {0-31}. The divide may be avoided in theimplementation and the distance value may be easily implemented inhardware using the following:d={[4*MAX(|dx|,|dy|)+MIN(|dx|,|dy|)]*DG+64}>>7This may produce values in the range {0-150} in an unsigned value.

Following the distance approximation block 307, there may be thethreshold block 309. In the threshold block 309, if(d<TH) then Diagonal Strength =0(d>=TH) then Diagonal Strength =dAs a result, depending on the threshold, weak edges in an image may getforced to zero and get treated as if there is no edge at all. The valueof the threshold TH may be programmable. If the diagonal strength is 0,the vertical FIR may be utilized by default.

The threshold block 309 may be adapted to force the follow-on diagonalfilter blend circuit to default to a simple 4-tap vertical filter inimages where the diagonal content may not be particularly strong. Theoutput signal diagonal strength 315 may be a value in the range {0-150}.

FIG. 4 illustrates a block diagram of an exemplary diagonal filter block400 that may be integrated in a directional filter, in accordance withan embodiment of the invention. The diagonal filter block 400 may be,for example, the diagonal filter block 211 of the directional filter 200of FIG. 2. The diagonal filter block 400 may utilize the input pixelvalues in addition to the angle selection signal 215 and diagonalstrength signal 217 outputted by the angle detection block 209 toimplement a 2-D x-y filter kernel, and blend with a vertical 4-tap FIG.The diagonal filter 400 may be adapted to output a single luma value asthe spatial average 411 every clock cycle. The diagonal filter 400 maycomprise a 2-D x-y filter 401, and a blend function 403.

The 2-D x-y kernel of diagonal filter 400 may be implemented with, forexample, a 5-pixel horizontal filter by 4-line vertical filter. The4-line vertical filter may be utilized to compute the N (north) FIRfilter; the remaining diagonal kernels may utilize a 5-pixel horizontalby 2-line vertical filter. The x-y kernel may output every cycle both avalue 405 for N (north) and a diagonal value 407 for one of the otherdirectional filters {NWW, NW, NNW, NNE, NE, NEE} depending upon theselected coefficients for {E⁻² E⁻¹ E₀ E₁ E₂} and {F⁻² F⁻¹ F_(0 l F) ₁F₂} based on the direction determined by the angle detection block 209.The selection of the filters may be determined using the angle selectionsignal 215 and may, for example, consist of the following choices:

$P = \begin{bmatrix} \circ & \circ & H & \circ & \circ \\E_{- 2} & E_{- 1} & E_{0} & E_{1} & E_{2} \\F_{- 2} & F_{- 1} & F_{0} & F_{1} & F_{2} \\ \circ & \circ & J & \circ & \circ \end{bmatrix}$

The table below illustrates exemplary directional interpolators that maybe utilized by the motion adaptive de-interlacer with integrateddirectional filter 200 based on the direction of the diagonal, inaccordance with an embodiment of the invention.

$\begin{matrix}{{Int}_{N} = \begin{bmatrix}0 & 0 & {- 0.046875} & 0 & 0 \\0 & 0 & 0.546875 & 0 & 0 \\0 & 0 & 0.546875 & 0 & 0 \\0 & 0 & {- 0.046875} & 0 & 0\end{bmatrix}} & \; \\{{Int}_{E} = \begin{bmatrix}0 & 0 & 0 & 0 & 0 \\0 & 0 & 0.5 & 0 & 0 \\0 & 0 & 0.5 & 0 & 0 \\0 & 0 & 0 & 0 & 0\end{bmatrix}} & \; \\{{Int}_{NE} = \begin{bmatrix}0 & 0 & 0 & 0 & 0 \\0 & 0 & 0 & 0.5 & 0 \\0 & 0.5 & 0 & 0 & 0 \\0 & 0 & 0 & 0 & 0\end{bmatrix}} & \; \\{{Int}_{NW} = \begin{bmatrix}0 & 0 & 0 & 0 & 0 \\0 & 0.5 & 0 & 0 & 0 \\0 & 0 & 0 & 0.5 & 0 \\0 & 0 & 0 & 0 & 0\end{bmatrix}} & \; \\{{Int}_{NNE} = \begin{bmatrix}0 & 0 & 0 & 0 & 0 \\0 & 0 & 0.25 & 0.25 & 0 \\0 & 0.25 & 0.25 & 0 & 0 \\0 & 0 & 0 & 0 & 0\end{bmatrix}} & \; \\{{Int}_{NNW} = \begin{bmatrix}0 & 0 & 0 & 0 & 0 \\0 & 0.25 & 0.25 & 0 & 0 \\0 & 0 & 0.25 & 0.25 & 0 \\0 & 0 & 0 & 0 & 0\end{bmatrix}} & \mspace{11mu} \\{{Int}_{NEE} = \begin{bmatrix}0 & 0 & 0 & 0 & 0 \\0 & 0 & 0 & 0.25 & 0.25 \\0.25 & 0.25 & 0 & 0 & 0 \\0 & 0 & 0 & 0 & 0\end{bmatrix}} & \; \\{{Int}_{NWW} = \begin{bmatrix}0 & 0 & 0 & 0 & 0 \\0.25 & 0.25 & 0 & 0 & 0 \\0 & 0 & 0 & 0.25 & 0.25 \\0 & 0 & 0 & 0 & 0\end{bmatrix}} & \;\end{matrix}$

The coefficients in the diagonal filter 400 may be implemented with, forexample, a simple shift and inversion in order to reduce hardware cost.A partial crossbar may be utilized to repeat pixels at the boundaries ofthe picture. This may apply to both the vertical N (north) filter and/orthe diagonal filter kernel selected for diagonal filtering.

The blend control parameter DS 409 may be derived from a select northsignal and the diagonal strength signal 217 from the angle detectionblock 209. The DS signal 409 may be driven to 0 when select north isactive, thus forcing the blend to select pure north (N) for the spatialaverage output 411. In other conditions, the DS signal 409 may be usedto merge midway between north (N) and diagonal filter (diag) dependingupon the diagonal strength. The spatial average output 411 may bedetermined in one of several ways using the blend control parameteralong with the diagonal filter and north signals.

Combining the directional filter 200 adaptively with de-interlacingtechnology may provide high quality stills with weave function, andproduce high quality motion with compass filter. Additionally, thedirectional filter may have unique angle detection capabilities, and mayblend multiple directions for smooth transitions in the source material.Accordingly, a method and system for motion adaptive de-interlacer withan integrated directional filter 200 may provide a better quality videosignal and a good complement to de-interlace processing for motion,while utilizing a low cost implementation.

Accordingly, the present invention may be realized in hardware,software, or a combination thereof. The present invention may berealized in a centralized fashion in at least one computer system, or ina distributed fashion where different elements may be spread acrossseveral interconnected computer systems. Any kind of computer system orother apparatus adapted for carrying out the methods described hereinmay be suited. A typical combination of hardware and software may be ageneral-purpose computer system with a computer program that, when beingloaded and executed, may control the computer system such that itcarries out the methods described herein.

The present invention may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

1. A system that determines the strength of an edge in a video image,the system comprising: a first processing circuitry that determines agradient of the edge in a first direction; a second processing circuitrythat determines a gradient of the edge in a second direction; a firstcircuitry that approximates a distance function using the gradient inthe first direction and the gradient in the second direction; a secondcircuitry that compares the distance function to a threshold; andwherein the strength of the edge is determined based on a result of thecomparison.
 2. The system according to claim 1 wherein the threshold isprogrammable.
 3. The system according to claim 1 wherein the edge isignored when the distance is less than the threshold.
 4. The systemaccording to claim 1 wherein the first processing circuitry comprises avertical edge detector.
 5. The system according to claim 1 wherein thesecond processing circuitry comprises a horizontal edge detector.
 6. Thesystem according to claim 1 wherein the first circuitry comprises adistance approximation block.
 7. The system according to claim 1 whereinthe second circuitry comprises a threshold block.
 8. A method thatdetermines the strength of an edge in a video image, the methodcomprising: determining a gradient of the edge in a first direction;determining a gradient of the edge in a second direction; approximatingthe distance function using the gradient in the first direction and thegradient in the second direction; comparing the distance function to athreshold; and determining the strength of the edge based on the resultof the comparison.
 9. The method according to claim 8 wherein thethreshold is programmable.
 10. The method according to claim 8 furthercomprising ignoring the edge when the distance function is less than thethreshold.
 11. The method according to claim 8 wherein the firstdirection is a horizontal direction.
 12. The method according to claim 8wherein the second direction is a vertical direction.
 13. The methodaccording to claim 8 wherein the approximated distance is anapproximated Cartesian distance.
 14. A computer-readable storage havingstored thereon, a computer program having at least one code section thatdetermines the strength of an edge in a video image, the at least onecode section being executable by a computer for causing the machine toperform steps comprising: determining a gradient of the edge in a firstdirection; determining a gradient of the edge in a second direction;approximating the distance function using the gradient in the firstdirection and the gradient in the second direction; comparing thedistance function to a threshold; and determining the strength of theedge based on the result of the comparison.
 15. The computer-readablestorage according to claim 14 wherein the threshold is programmable. 16.The computer-readable storage according to claim 14 further comprisingcode for ignoring the edge when the distance function is less than thethreshold.
 17. The computer-readable storage according to claim 14wherein the first direction is a horizontal direction.
 18. Thecomputer-readable storage according to claim 14 wherein the seconddirection is a vertical direction.
 19. The computer-readable storageaccording to claim 14 wherein the approximated distance is anapproximated Cartesian distance.
 20. A method that approximates aCartesian distance of a point from an origin of a plane in which thepoint lies, the method comprising: determining a first coordinate of thepoint in a first direction; determining a second coordinate of the pointin a second direction; determining a maximum of an absolute value of thefirst coordinate and an absolute value of the second coordinate;determining a minimum of the absolute value of the first coordinate andthe absolute value of the second coordinate; and using the maximum andthe minimum to approximate the Cartesian distance function of the pointfrom the origin.